The security of vessels, both military and commercial, as well as other assets located in and around seaports, has been of increasing concern in the wake of activities by terrorists and others. Most security efforts have focused on potential land-based attacks, and little attention has been devoted to the provision of an effective deterrent to assaults from floating objects, vessels or other water-based threats.
A vessel anchored at port to take on fuel or supplies is particularly vulnerable to attack. Although radar, sonar and other sensors can remain active and manned during these periods, no evasive action could be taken in a short period of time to avoid a water-born attack. One option for military vessels is to remain on alert while anchored, with guns manned, but in busy seaports it may be difficult to discern between harmless commercial traffic and a potential attacker. At present, there is no system which is visible in the water for effectively defining an area of restricted access and to warn other vessels to stay away from a military or commercial ship at anchor. Buoys, channel markers and the like which are commonly found in the water at seaports are not suitable for use as a warning device because they have not historically been used for such purpose and would not be perceived in that way by vessel operators. As a consequence, it is conceivable that an innocent commercial vessel could be fired upon by an anchored military ship for entering restricted space defined by buoys or other markers because the vessel operator did not realize the buoys or markers were being used for that purpose.